TERZ 91

Electronic Turbine Meter
TERZ 91
RMG Meßtechnik GmbH
Publication No. 3.173-E
P.O.Box 280 · D-35502 Butzbach
Phone +49(0)6033 897-0 · Fax +49(0)6033 897-130
E-Mail: messtechnik@rmg.de · Internet: http://www.rmg.de
Innovative equipment for
high-precision gas metering

1. Function
The electronic turbine meter TERZ 91 is a flow meter
directly measuring the volume flow rate of gases at
actual conditions. The flow rate measured and the
volume are displayed on an electronic index head.
The method of operation of the meter is based on
velocity measurement using a turbine wheel. The gas
flow passes the ring-shaped inlet section of the flow
straightener and reaches the coaxially mounted
turbine wheel, whose speed is proportional to the
mean velocity of the gas flow within the scope of the
measuring range.
The speed of the turbine wheel is recorded inductively
using non-contact measurement by a pulse-wire
sensor and a permanent magnet. Due to the fact that
the signal frequency is directly picked up at the turbine
wheel, the meter is also suitable for control
applications.
2.
Construction
The electronic turbine meters form a series of uniform
construction. Each meter consists of four structural
units (see drawing). An aerodynamic flow straightener
fitted into the meter case constricts the effective cross
section of the pipe to form a ring-shaped crosssectional
area and substantially eliminates
turbulences. This increases the velocity of the flowing
gas. The shaft mounted with ball-bearings carries the
turbine wheel on the one side and a permanent
magnet rotating before the sensor on the other. The
duct of the sensor sleeve towards the unpressurized
section of the index head is sealed off by a pressuretight
O-ring. By means of the setscrew the index head
can be fixed in the most favourable position for taking
readings.
Index head
O-ring
Sensor sleeve
Setscrew
O-ring
Sensor
Flow straightener
Permanent magnet
Turbine wheel
Ball bearing
3. Types of gases
The TERZ 91 standard design is suitable for all gases
complying with the DVGW working sheet G260. The
materials used are appropriate for gases and fuel
gases, such as natural gas, refinery gas, liquid gases
and their mixtures, nitrogen, CO (dry), air and all
2
inert gases.
For aggressive and chemical gases, there are special
designs available with PTFE lining, special material,
special lubrication, etc.

max
max
min
4. Characteristics
For secondary metering
Electronic totalizers
(Main totalizer, additionally start/stop or resettable
totalizer)
Battery mode (with Type TERZ 91)
Service life of the battery is a minimum of 6 years
4-20 mA current output
(with Type TERZ 91-S)
Low-torque metering system with long-term
stability
(apart from the turbine wheel, there are no
mechanically actuated parts)
LF and HF pulse outputs
(The pulse value of the LF pulse output can be
adjusted)
Intrinsically safe circuit, approved for zone 1
Degree of protection: IP 65
Flow display
Option for external disablement of the counting
mechanism
(in order to suppress overtravel)
Compact construction with a rotatable counter
head
Option for use as a remote counting mechanism
5. Approvals
EEx ib II C T4
as per certificate of conformity No.: Ex 96.D.2041
DVGW product ident No. CE-0085BN0292
6. Electronic index head
Possible connections of the electronic index head:
HF pulse output
(high frequency)
direct signal frequency
Transistor, open collector
as per NAMUR specification
U = 13.5 V (Ex)
30 V (non Ex)
LF pulse output
(low frequency)
decade-scaled
Transistor, open collector
as per NAMUR specification
Switch input
for stopping the totalizer
voltage-controlled
(optocoupler)
4-20 mA current output
Type TERZ 91-S
(option)
max U max = 13.5 V (Ex)
Totalizer stop:
U max = 30 V
30 V (non Ex) 5V

7 . Overview
Nominal size Measuring range Pulse value Pressure loss Lubrication
Q min -Q max
LF 1) HF 2) p
mm in. m 3/h
pulses/m 3 pulses/m 3 mbar permanently
lubricated
oil pump
25
40
50
1
1½
2
2.5 -
5-
6-
25
70
100
10/100
1/10/100
1/10/100
13450
7800
7800
3
4
5
•
•
•
80
100
150
200
250
300
400
500
600
3
4
6
8
10
12
16
20
24
10 -
25 -
40 -
100 -
160 -
250 -
400 -
650 -
1000 -
250
400
1000
1600
2500
4000
6500
10000
16000
0.1/ 1/10
0.1/ 1/10
0.1/ 1/10
0.1/ 1
0.1/ 1
0.1/ 1
0.1/1
0.1/1
0.01/ 0.1
2375
1060
330
135
75
48
24
12
6
6
4
6
3
3
4
3
4
4
•
•
•
•
•
•
•
•
•
3
4
6
8
10
12
16
20
24
25 -
40 -
100 -
160 -
250 -
400 -
650 -
1000 -
1600 -
400
650
1600
2500
4000
6500
10000
16000
25000
0.1/ 1
0.1/ 1/10
0.1/ 1
0.1/ 1
0.1/ 1
0.1/ 1
0.1/1
0.01/ 0.1
0.01/ 0.1
1250
600
190
80
44
28
14
7
4
14
10
12
8
7
9
8
9
9
•
•
•
•
•
•
•
•
•
1) Standard values (set in the factory) are shown in bold type
2) Approximate value; the exact value is determined during calibration
8. Pressure loss
The pressure loss p stated in the table applies to natural
gas at Qmax
and under 1 bar. From this, the pressure loss
at actual conditions can be calculated in accordance with
the formula below.
Pressure loss as per the formula
2
p = p n Q
a • • p a
a •
0.81 ( Qmax )
p
a = Pressure loss at actual conditions (p a, Q a) in
mbar
p = Pressure loss at Qmax
and natural gas at 1 bar
in mbar (see table)
n
= Standard density of the process gas (kg/m 3)
p a = Pressure at actual conditions in bar (absolute)
Q a = Flow rate at actual conditions (m 3/h)
Q = Maximum flow rate
max
Example: Air, nominal meter size DN 100, measuring
range 20 - 400 m 3/h,
p a = 1.1 bar(abs),
n
= 1.29 kg/m 3, Q a = 250 m 3/h
take from the table: p = 4 mbar
Hence:
1.29 250
p a = 4 • • 1.1 • = 2.74 mbar
0.81 400
9. Measuring accuracy
Measuring error: ± 2% for Qmin to 0.2 · Qmax
± 1% for 0.2 · Qmax
to Qmax
(DN 25: ± 2% for Qmin
to Q max)
Reproducibility: ± 0.5%
10. Maintenance
( )
All turbine meters up to and including the nominal size of
DN 150 are fitted with permanently lubricated bearings
and require no maintenance. From the nominal size of
DN 200, the meters are fitted with a lubricator.
Lubrication is to be performed in compliance with the
operating instructions (see also lubrication instruction
plate at the meter).
2

11. Types of construction and dimensions
A
A
A
A
B
C
B
C
B
C
B
C
L
L
L
L
Flanged-end Design ( F)
Sandwich design ( S)
Monoflange design ( M)
Threaded-end design ( G)
(Adaptor-flange mounting)
(only aluminium cases)
Weights and measures
Pressure stages
Case Nominal L A B C Weight PN 10 PN 25 PN 40 ANSI 300 PN 64
design size mm mm mm mm kg PN 16 ANSI 150 PN 100
mm ANSI 600
G
25
1)
185 80 145 195 4 Alu
Threads 40 2) 140 80 145 195 4 Alu
50 150 60 180 265 10 • • • •
80 120 35 215 315 14 • • •
100 150 50 225 345 25 • • •
150 175 70 255 410 40 • • •
200 200 70 280 470 60 • • •
F
250 300 135 320 540 70 • •
300 95 325 580 100 • •
300
450 200 325 610 200
• • •
Flanges 400 145 335 650 180 • •
400
600 345 335 680 400
• • •
500
400 110 385 760 300 • •
750 260 385 810 650
• • •
600
600 130 440 870 400 • •
900 280 440 920 850
•
50 80 60 175 255 15
•
80 120 35 200 300 35
• •
M 100 150 50 225 355 50
• •
Mono- 150 175 70 270 445 100
• •
flanges 200 200 70 305 510 130
• •
250 250 85 345 590 200
• • •
50 80 30 145 195 123)
Alu •
80 120 30 200 280 20 • •
100 150 50 220 330 30 • •
S
150 175 70 250 400 50 • •
Sandwich 200 200 70 280 450 70 • •
250 250 85 315 530 110 • •
1) External thread R 1½"; with coupling kit: internal thread Rp1 ISO 7-1, overall length 243 mm
2) External thread R 2¼"; with coupling kit: internal thread Rp1½ ISO 7-1, overall length 206 mm
3) 4 kg for PN 10 and PN 16 (aluminium case)
Special designs on request

max
max
min
Weitere Daten:
Schalter drücken
MESSTECHNIK GMBH
35510 Butzbach
Electronic Turbine Meter
TERZ 91
12. Options for mounting the index head
By mounting the electronic index head in different ways,
optimum readings can be taken in any position. If no
special type of installation is specified, the index head is
to be installed in accordance with the figure below.
00064419
F 1.4
Standard design
Electronic Turbine Meter
Type TERZ 91
Volume
00064419 m³
F 1.4 m³/h Index head
Flow rate
p
bar DN
Q
m³/h No.
Q
m³/h Yr.
LIYCY cable
2x0.75 blue
00064419
F 1.4
00064419
F 1.4
max. cable length: 50 m
Options for mounting the index head
Remote index
Measuring
element
13. Mounting and operating instructions
TERZ 91 turbine meters can be operated in any position
up to the nominal size of DN 200. From the nominal size
of DN 250, they can only be installed in a horizontal
position. By loosening the setscrew, the index head can
be rotated by 360° to achieve an optimum position for
taking readings. In the event of difficult mounting
conditions, the counter head can also be installed
separately as a remote index. It is also possible to retrofit
the TERZ 91 turbine meter as a remote index.
Special instructions for start-up and operation:
Caution!
Turbine meters are precise measuring instruments
and must be carefully handled during transport,
storage and operation.
Do not fill any downstream pipelines or station
sections via the turbine meter. This may result in
excesive flow rates with resultant damage to the
turbine wheel.
The meter has been designed for short-time overload
operation at up to 1.2 times the value of Q max. However,
such load conditions should be avoided in order to
protect the TERZ 91 from any unnecessary high load.
The gas flow must be free of shocks and pulsations as
well as free of foreign particles, dust and liquids.
Otherwise it is recommended that filters and separators
be installed.
Avoid any components fitted directly upstream of the
turbine meter which would affect the gas flow (see
DVGW guidelines and PTB guideline G 13).
The meter must be installed in weather-proof locations.
For outside installations, appropriate guards must be
provided against direct weathering influences. The
TERZ 91 can be used at following temperatures:
Temperature range of fluids: -20°
C bis +60°C
Ambient temperature range: -20°C bis +50°C
Special designs for higher and lower temperatures are
available.
RMG Meßtechnik GmbH
Publication No. 3.173-E
P.O.Box 280 · D-35502 Butzbach
Telefon +49 (0)6033 897-0 · Fax +49 (0)6033 897-130
E-Mail: messtechnik@rmg.de · Internet: http://www.rmg.de
Status 04/2003
Subject to technical change